The oral cavity is populated by a prodigious microbial flora that exhibits a unique successional colonization of enamel and subgingival root surfaces. A wide range of oral sites provide different ecologic conditions and are, therefore, populated by different commensal microbial combinations. The sequence of microbial colonization, regardless of location within the oral cavity, commences with the acquisition of salivary and/or crevicular fluid-derived pellicle.
As the process of successional microbial colonization of the gingival crevice and gingival margin proceeds uninterrupted, achieving critical mass between 5 and 10 days, gingivitis becomes evident at a clinical level. However, at a histologic level, gingivitis may be evident within 2 to 4 days of plaque accumulation. The inflammatory process sufficiently alters the ecological conditions so as to allow proliferation of supragingival plaque into subgingival areas. The subgingival plaque becomes progressively more Gram-negative and anaerobic in nature as the periodontal pocket deepens, leading ultimately to a chronic, progressive deterioration of the periodontium, referred to as adult periodontitis.
Brushing of the teeth is the most commonly used method for patient-facilitated removal of the dental microbial plaque. However, dental microbial plaque is frequently located in areas that prohibit its removal. This is particularly evident in such areas as the interproximal subgingival region. The bristles tips of an ordinary manual toothbrush and even automatic electromechanical toothbrushes cannot penetrate such areas, thereby allowing microbial plaque to accumulate, ultimately reaching critical mass, and inducing a host inflammatory response that leads to the common periodontal diseases (e.g., gingivitis and adult periodontitis).
Dr. Philipp G. Woog, one of the coinventors herein, invented the first automatic toothbrush and, after over 40 years of experience, firmly believes that a major cause of periodontal disease is absence of firmer and harder foods in modern day diets that would necessitate and require more deliberate and aggressive biting that would ensue in more exercise of the gums. Modern soft and refined foods require very little biting and other than firm fruit, modern foods including meats are generally soft. Dr. Woog believes certain groups of people with healthy gums such as the Yanomani Indians and Eskimos have healthy gums because raw vegetables and dry meat are common to their diets. These foods require biting that will inevitably result in pressure being applied to gums with attendant exercise and manipulation thereof because the gums under these circumstances will ride up on the upper teeth and down on the lower teeth.
Because conventional tooth brushing (manual and automatic) relies on direct contact between the brush bristle and the tooth surface to remove microbial plaque accumulations, those interproximal and subgingival areas that allow only limited or no access to bristle tips will generally exhibit undisturbed plaque formation. The sonic toothbrush was conceived in an attempt to overcome the problems presented by lack of access during manual toothbrushing--particularly the concept of cleaning beyond the bristles due to the acoustic effects generated at sonic frequencies being transmitted by the fluid environment that is associated with teeth during the act of toothbrushing.
Very recent and serious studies have shown that through the medium of a coupling fluid (saliva, toothpaste, etc.) the tips of the bristles of an electric toothbrush moving at a speed or a velocity of 1.5 m/s, create a reciprocating acoustic pressure and a shear stress, which effectively works to remove the dental plaque from the enamel surface at a distance of 2 mm beyond the bristle tips without bristle/tooth contact. This permits reaching very narrow spaces such as interdental spaces which even very thin bristles can hardly reach.
There are currently two known sonic automatic toothbrushes that have been commercialized under the names SONICARE and SENSONIC. The SONICARE device is purportedly marketed under U.S. Pat. No. 5,378,153 and the Sensonic device is allegedly quite similar. These devices claim to produce sonic vibrations, or low frequency acoustic energy, to enhance removal of bacterial plaque in vitro at distances beyond filaments. However, there appears to be little clinical data to support these in vitro findings.
The concept of sonic toothbrushes is based on the production of an acoustic effect being mediated through a liquid environment. However, patients do not brush their teeth by holding the brush tips 2 mm off of the tooth surface. Most users of the aforenoted sonic automatic toothbrushes place or force the brush tips against the tooth surfaces with various degrees of pressure. In fact, by placing the brush bristle against the tooth a severe dampening effect of sonic wave production occurs. This dampening effect could not only severely reduces the frequency of the sonic wave and therefore the acoustic effect, but also severely alters the phase of movement of the bristle tips, i.e., reducing the movement cycles per unit time of the bristle tip versus that at the bristle power source. In actual practice, the end result is a sonic tooth brush by design that has been converted to a highly efficient non sonic, mechanical brush in actual use. Any difference in clinical trials of the current sonic brushes versus mechanical and/or manual tooth brushes is likely a manifestation of the increased number of bristle cycles per unit time (more contact with the tooth surface) and not a result of acoustical effects.
It has been found that the torque and power level determines the effectiveness of cleaning and gum massaging with sonic automatic toothbrushes. An additional fundamental parameter, which should not be neglected is that an automatic toothbrush is not a simple "washing machine, but also and mainly a gum massaging instrument as well as a teeth brushing device by direct mechanical action (tooth enamel polishing, dislodging of wedged food particles, etc.).
To comply with these last requirements it is mandatory to introduce the notion of power under load, in other words, mechanical power at the level of the bristle tips under an applied force of about 350 g 3.5 N! against teeth and gums. It is under these conditions of load that the power must be sufficient to guarantee an acceptable amplitude of motion and frequency, and consequently velocity to offset any dampening of sonic energy.
It has also been determined that a practical technical solution to obtain an effective mechanical brushing power several times the one of existing electric toothbrushes and in order to assure sonic level of energy is to use a hydraulically powered toothbrush, as for example of the type disclosed in U.S. Pat. No. 4,561,251 and sold in the U.S. under the trademark "Woog Perio System" and "Periobrush" and supply it with boosted or increased parameter so that the bristle velocity, acoustic pressure and shear stress is constant and not dramatically reduced below critical values with applied forces increasing from 0 g to the relatively high value of 350 g. However, the Perio System toothbrush is somewhat inconvenient because it is bulky, heavy, and too big to carry. It is expensive and consumes high power while being complicated and of low reliability.